Highly oriented single-phase blend films of high- and low-density polyethylene

The microstructures of highly oriented drawn films of blends of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) were investigated by transmission electron microscopy, electron diffraction, X-ray diffraction, and differential scanning calorimetry (DSC). The average crystal size, as well as long period, crystalline content, and melting endotherm peak, decreased as LDPE was added to the blend. When the LDPE content exceeded ～ 50%, the film texture changed from a single crystal texture to fibre symmetric. Segregation of the two polyethylenes was not detected at low LDPE contents in as-drawn or melted and recrystallized films. In the as-drawn films, a low temperature tail began to appear on endotherm melting peaks at LDPE contents ?70%, indicating the onset of segregation. In meltcrystallized films, however, two distinct melting endotherm peaks were visible for LDPE contents ?50%. An equilibrium melting point of 141° C and end surface free energy of 101 erg cm^?2 (101 × 10^?7 J cm^?2) were determined by use of the Thomson equation. The close agreement between these values and literature values for HDPE suggested that the crystals present in HDPE/LDPE blends were thermodynamically equivalent to HDPE crystals of equal size, implying that branches were excluded from the crystalline phase.     

Distinctive Features of Water–Dimethyl Sulfoxide Mixtures: Dielectric Spectra Revisited

Broadband dielectric spectra (1 MHz to 80 GHz) are reported for dimethyl sulfoxide–water mixtures in the complete composition range. The spectra are evaluated in order to yield information about the underlying relaxation time distribution, the principal relaxation time, and the static permittivity of the liquids. With a view of gaining insights into the structure and microdynamics of water in its different states of interaction, these parameters are compared to such for mixtures of water with other protic and aprotic dipolar liquids as well as with non-polar substances. Also used for information about structure fluctuations are ultrasonic spectra of the dimethyl sulfoxide–water system (0.2 MHz to 2.75 GHz). A notable result is the composition dependence of the principal dielectric relaxation time. In conformity with the wait-and-switch model, it increases at low DMSO content and thus reflects the decrement in the concentration of hydrogen-bonding sites. The decreasing relaxation time at high DMSO content is clearly a result of the reduced association due to the reduced concentration of hydrogen-donating sites.     

Asphalt concrete modification with waste PMMA/ATH

This paper presents recycling of waste PMMA/ATH powder in asphalt concrete mixture. Waste PMMA/ATH is generated in large amounts during shaping process of acrylic sheets. Recycling waste polymers rationally and efficiently has become one of the priorities of road pavement industry in recent years. Therefore, in this study waste PMMA/ATH powder was incorporated in an asphalt mixture. In one case waste PMMA/ATH was used as an asphalt binder modifier and in other case as a partial replacement for fine aggregate fraction. Basic performance characteristics of asphalt mixtures were evaluated by measuring material properties such as rutting potential and stripping resistance. Binder characteristics were determined also on artificially aged samples. With both modification methods, improved performance characteristics of asphalt mixture were achieved which can increase road pavement durability. Finally, waste PMMA/ATH allowed us to prepare an asphalt mixture that had strongly enhanced mechanical properties regarding to the wheel tracking test and could also have less negative effects on the environment as indicated by moisture susceptibility test results.     

Effects of SEBS-g-MA copolymer on non-isothermal crystallization kinetics of polypropylene

The non-isothermal crystallization kinetics of pure PP and PP/SEBS-g-MA blends up to volume fraction, Φ _d (0–0.50) was studied by differential scanning calorimetry at four different cooling rates. Crystallization parameters were analyzed by Ozawa and Liu models. The Ozawa model fits in the PP/SEBS-g-MA blends and indicates the effect of SEBS-g-MA copolymer on the crystallization process of polypropylene. Augis–Bennet model has been used to calculate activation energy, ?E, during non-isothermal crystallization process. The value of ?E decreased with SEBS-g-MA due to flexibility of SEBS-g-MA by which movements of chains of PP become easier.     

Investigation of phase intergrowth morphologies in the system Zn2SiO4-SiO2 by photo-emission electron microscopy

By means of photo-emission electron microscopy, which is described briefly, X-ray diffraction and electron microprobe analysis the hypo- and hypereutectic solidification in the system Zn₂SiO₄-SiO₂ has been investigated. Faceted (idiomorphic) growth of stableα? and metastableΒ-zinc silicate with some excess SiO₂ on the hypoeutectic side of the phase diagram and a metastable region of liquid immiscibility on the SiO₂-rich (hypereutectic) side determine the respective phase intergrowth morphologies. Unconstrained eutectic solidification causes a “divorced eutectic” where the zinc silicate constituent grows first from the undercooled liquid, which is simultaneously enriched in SiO₂.     

Structure of reconstituted collagen hollow fibre membranes

Small- and wide-angle X-ray scattering (SAXS and WAXS) methods were employed to study the structure of reconstituted collagen hollow fibre membranes and the changes that ensue upon entry of water. The tails of the SAXS curves were analysed and were shown to obey Porod's Law. WAXS and water absorption measurements as a function of relative humidity were combined with density measurements to determine the relative volume fractions of water in the “free” and “bound” states. Treating the hollow fibre as a two phase system and employing Porod's Law, average length parameters transverse to the fibre axis were extracted for the collagen fibrils and the water filled pores. All this information was synthesized to yield a model of the structural changes in the hollow fibre caused by water. Implications of such a model for qualitative and quantitative prediction of changes in properties were studied.     

Performance improvement of pentacene organic field-effect transistor through introducing polymer buffer layers

Pentacene organic field-effect transistors (OFETs) employing poly(methyl methacrylate) (PMMA), polystyrene and polyvinylidene fluoride as the electrode buffer layers by simple spray-coating fabrication process were systematically investigated. Significant performance enhancement of the OFETs was obtained. By analyzing the morphologies of pentacene films grown on gold electrodes and the electrical characteristics of these OFETs, the performance improvement was attributed to the uniform and hydrophobic properties of polymer surface, leading to a remarkable reduction of contact resistance at the pentacene/electrodes interface. Moreover, the results showed that the device employing PMMA as the electrode buffer layer exhibited the highest hole mobility of 0.59 cm²/Vs, which was almost five times of the control one. Such effect was ascribed to the optimal surface energy and appropriate dielectric constant of PMMA, which were favorable for the growth of pentacene crystal and responsible for the highest performance of OFET using PMMA as the electrode buffer layer.     

Magnetic and Structural Study of FeNi3 Nanoparticles: Effect of Calcination Temperature

Bimetallic Fe–Ni alloy nanoparticles (NPs) with molar ratio of Fe to Ni 1:3 were synthesized via chemical reduction using hydrazine in aqueous solution and then calcined at different temperatures. The prepared NPs have been characterized utilizing X-ray diffraction (XRD), energy-dispersive X-ray (EDS) spectroscopy, and vibrating sample magnetometer (VSM). XRD results show that FeNi₃ NPs with face-centered cubic (FCC) crystalline structure were formed. FeNi₃ phase completely disappeared and pure NiO and NiFe₂O₄ phases observed on further heating at 550° C. VSM results reveal a superparamagnetic characteristic for the synthesized NPs when calcined at 50° C. An increased coercivity and decreased saturation magnetization has been observed with increasing calcination temperature up to 550° C.     

Tensile failure mechanisms in carbon fibre reinforced plastics

Tensile failure mechanisms in type I carbon fibre-reinforced epoxy resin have been studied by examining the modes of failure of cured and semi-cured CFRP and of fibre bundle specimens. The rigid matrix in the cured material modified the appearance of the fractured specimen but by detecting the acoustic emission generated during loading the basic fibre bundle behaviour was found to exert a major influence on fracture. Microscopic examination of fractured CFRP specimens has revealed that consecutive fibre failure may be restricted to sub-bundles as a result of shearing between these sub-bundles, and that the material is weakened by a number of internal failures that are not necessarily connected. Ultimate failure seems to be statistically determined and it is a characteristic of the material that some scatter in the strength of CFRP must be expected.     

Synthesis and characterization of a new type of electro-optic polymer without carbon main chains

A new type of electro-optic (EO) polymer is prepared in this work. The main chain of the EO polymer is made of polyphosphazenes, and the side chain consists of carbazole based nitro azobenzene. The principle and method of preparation are given and the characteristics of this material are studied in details. The polymer with an EO coefficient of 35 pm/V has fine stability and can be easily processed. It also shows photoconductivity due to the carbazole group. This polymer thin film is obtained through performance improvement. Terahertz (THz) wave can be detected using the device, which is made of the new polymer. Owing to its fascinating properties, this new type of EO polymer has the potential to be widely applied in photorefractive materials as well as for emission and detection of THz radiation.     

Flux growth of silicates with vapour transported silicon

As a result of a proposed vapour transport mechanism, silicate crystals have been grown from fluxed melts which originally contained only trace amounts of silicon. The melts were contained in platinum crucibles in a sillimanite, Al₂SiO₅, muffle, and the flux consisted of PbF₂, or PbF₂ + PbO, occasionally with additional MoO₃. It is postulated that a volatile siliceous species resulted from the reaction of PbF₂ vapour with the muffle and that this species transported Si into the fluxed melts. The silicate crystals produced include Er₂SiO₅, Dy₂SiO₅, Mg₂SiO₄·MgF₂, a new material of formula Dy₄SiO₈, and several new rare earth compounds with the apatite structure.     

Nanoscale structuration and optical properties of thin gold films on textured FTO

In this work, we propose a methodology to synthesize metallic nanoparticles on textured Fluorine Tin Oxide (FTO) surface by laser irradiations of deposited Au films. In particular, the breakup of the Au films into nanoparticles (NPs) is observed as a consequence of the melting and solidification processes induced by laser irradiations. The mean Au NPs size and surface density evolution are analyzed as a function of the laser fluence. Optical characterizations of the glass/FTO/Au NPs multilayer show, in the absorption spectra, plasmonic peaks due to the Au NPs and an improvement of the light absorption efficiency from the sample with larger Au NPs. The simulated trends of the ratio between the scattering and absorption cross section suggest that the absorption efficiency dominates over the scattering efficiency in the spectral range between 200 and 600 nm. The simulation shows that, by varying the NPs radius from about 18 to 24 nm, the radiation-scattered intensity remains symmetric in forward and reverse directions. These results indicate that the surface coverage size distribution of Au NPs is the key parameter to correlate the structural and optical properties of the glass/FTO/Au NPs multilayer. Furthermore, electrical characterizations highlight a reduction in the sheet resistance of the textured FTO due to the presence of the NPs. We compare these results with those obtained for the same systems when standard furnace annealing processes are used to obtain the Au NPs on the textured FTO surface.     

An infrared spectroscopic study of vacuum-evaporated SiO-CeO2 thin films

Infrared spectra of vacuum-evaporated SiO-CeO₂ thin films are reported for a series of thin films of varying compositions. They show a systematic shift of the SiO “O stretch” frequency from a value of 1040 cm^?1 in the pure (100 mol %) SiO film to 950 cm^?1 in the 16 mol % SiO84 mol % CeO₂ film, as well as a gradual diminishing of the band at 876 cm^?1 with increasing CeO₂ concentration. After introducing the general perspective for the analysis of the infrared spectra of amorphous solids, and tetrahedrally bonded compounds in particular, it is proposed that the first two features of the spectra result from a chemical association between nonbridging oxygen atoms of the SiO network and cerium atoms. This entails the interpretation of the band at 876 cm^?1 as being due to the stretching vibrations of the non-bridging oxygen atoms. The effect of annealing on the spectra is also presented and explained in terms of creation of new Si-O-Si linkages.     

The use of foreign patenting as an internationally comparable science and technology output indicator

Foreign patenting activity in some of the world major patent systems is being compared between countries and industries and is found to be, with a few notable exceptions, relatively unbiased. Furthermore, a brief dynamic analysis of the foreign patenting activity in the USA of a number of OECD-countries in 41 industrial sectors in terms of ‘Revealed Technological Advantage’ indices suggests that foreign patent data might provide a very useful addition to the arsenal of Science and Technology Output Indicators.     

Interfacial energetics in the TD-nickel and TD-nichrome systems

The absolute (mean) interfacial free energies are measured in thoria-dispersed (2 vol %) (TD)-nickel and the TD-nichrome (Ni-20% Cr) systems at 1200° C utilizing techniques of scanning electron and transmission electron microscopy. Values of particle/matrix interfacial energies for TD-NiCr and TD-Ni were measured at 2300 and 2000 erg cm^?2 respectively based upon measured values of 2040 and 2200 erg cm^?2 for the surface free energies for nichrome (80∶20 NiCr) and pure nickel respectively, by the method of zero creep and the measurement of grain-boundary groove angles in the electron microscope. Values of 900 erg cm^?2 and 1040 erg cm^?2 were measured for the surface and grain-boundary free energies for thoria (ThO₂). The particle/matrix adhesive energy for TD-nichrome was measured to be roughly half that for the TD-nickel system based upon the classical interfacial adhesion concept. It is concluded that the apparent difference in particle/matrix interfacial strength between TD-nickel and TD-nichrome results by a more complex mechanism than simple interfacial decohesion involving phase separation.     

Mechanical property enhancement of PVDF/graphene composite based on a high-quality graphene

In this paper, we adopted hot-pressing treatment to convert the regular reduced graphene oxide (RGO) from chemical exfoliation to the high-quality graphene (HQG), and then the HQG/poly vinylidene fluoride (PVDF) composite films were prepared by spin coating. The microstructural characterizations and property measurements revealed that (1) The HQG was free of defects and oxygen-containing functional groups on the surface, and exhibited a homogeneous dispersion and a well composite with PVDF; (2) The storage modulus of the HQG/PVDF composite was nearly twice higher than that of RGO/PVDF composite, and eight times higher than that of pure PVDF; and (3) The optimum additive amount of HQG with PVDF was at between 3 and 5 wt%. It is expected that the present HQG has a potential applications in polymer composites.     

Synthesis,structural and optical characterization of ZrO2 core–ZnO@SiO2 shell nanoparticles prepared using co-precipitation method for opto-electronic applications

Nanocrystalline Zirconia (ZrO₂) and Zinc oxide (ZnO) as well as Silica (SiO₂) coated ZrO₂ core–shell structures were synthesized by both Co-precipitation and seeded polymerization technique. The phase analysis and the core–shell structure formation were confirmed by X-ray diffraction (XRD), FESEM and high resolution transmission electron microscopy (HRTEM) analysis. The existence of SiO₂ on ZrO₂@ZnO was characterized by FT-IR measurement. UV–Vis study reveals coating of ZnO over Zirconia shows red shift in the absorption spectra. Photoluminescence studies show the non-monotonous variation in luminescence behavior of these core–shell nanoparticles. This investigation explains that the interfacial effect between the core (ZrO₂) and the shell materials (ZnO and SiO₂) can be exploited to tune the optical properties of the material. This implies that we can envisage the core–shell materials as potential candidates for optical–electronic devices.     

Crack patterns in cylinders explosively loaded at an hemispherical end

The final crack and fracture damage found in hemispherically-ended ‘Perspex’ (PMMA) rods loaded explosively by electrical detonators at their hemispherical end is described. The mechanisms of the formation of the major features are also considered. The most significant feature observed occurs as a Hertzian cone crack which develops to form a completely closed crack surface in the shape of a cardioid (heart-shape) solid of revolution. Also associated with these features are small areas of crazing and spalling generated by stress wave reflections.     

Study on electromechanical characterization of piezoelectric polymer PVDF in low-frequency band

Polyvinylidene fluoride (PVDF), a piezoelectric polymer material, is well known as one of the best smart materials to be used for tactile sensors in robots for its good performance. It has been used in many applications including sensors, actuators and surface acoustic wave (SAW) devices. This paper presents an experimental setup and experimental procedures for studying the electromechanical characterization of piezoelectric polymer films, by which the electromechanical characterization of the PVDF films under quasi-static loads and dynamic loads in a wide range of frequency can be researched. Through quasi-static tests, the stress–strain relationships of PVDF films in different directions were obtained. Furthermore, the viscoelastic and piezoelectric properties of PVDF films were analyzed based on the measurement results of dynamic tests under low frequency from 5 Hz to 200 Hz, and some suggestions of the applications of PVDF piezoelectric films in robot tactile sensor are presented.     

Thermo-optical,DSC and microfractographic investigation of PE-PE mixtures

The nucleation effect of high-density polyethylene (HDPE) to low-density polyethylene (LDPE) and the structure of the resulting directional LDPE morphology was studied using thermo-optics, differential scanning calorimetry (DSC), X-ray diffraction and microfractography. Thermo-optics and DSC showed a higher nucleation activity of HDPE compared with the heterogeneities within the LDPE melt. The parallel and more perfect arrangement of the chain segments in transcrystalline LDPE resulted in a higher melting temperature, a difference in unit-cell spacing and a less ductile behaviour during fracture than with spherulitic LDPE.